# Maths, Divine International Public School

If 15Cot=8, find (1+SinA)(1-SinA)/(1+CosA)(1-CosA)

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1. cotA = 8/15
tanA = 15/8
so y=15, x=8
r^2 = 15^2 + 8^2
r = โ289 = 17

sinA = 15/17
cosA = 8/17

then (1+SinA)(1-SinA)/(1+CosA)(1-CosA)
= (1 - sin^2 A)/(1 - cos^2 A)
= (1 - 225/289)/(1 - 64/289)
= (64/289) / (225/289)
= 64/225

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posted by Reiny

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